[问答题]
1.Outline the events which wqs-s,gr v)6 ztcx;c,to 9bh/f(s5 sv sould lead to an individuo a.fhkofbkm:p z0w , zp/y.)3al being born with Down syndrome, which is characterised by the presence of three copies of chromosome f oo:kyba hp zm3w.)p kz0,f./21.
